Metabolism

White-Nose Syndrome (WNS) effects on Bat Populations

Bat Populations across North America have been dwindling over the past decade due to the introduction of Pseudogymnoascus destructans, also known as White-Nose Syndrome (WNS).  This pathogen is a fungal disease that originated in Eurasia before it was introduced to the United States.  The first confirmed case of White-Nose Syndrome was in 2007, when scientists discovered many dead bats in a cave in Albany, New York. However, there were earlier suspected cases from 2005 to 2006.  The exact cause of the fungal disease’s introduction to North America is still unknown, though most scientists agree that its origin was likely linked to humans indirectly (Hoyt et al., 2021).

The disease has spread all over North America at a rate of 200 km/year to 900 km/year in the first eight years.  This is now in 39 states in the US and 7 Canadian provinces. WNS is typically spread to bats through direct contact with infected individuals or environments.  Figure 1 below shows the cycle of how the disease spreads.  The graph in Figure 1 indicates that the disease infections begin in August/September and begin to peak in November/December.  WNS will persist through winter and decrease around May when spring approaches.  This coincides with bats’ hibernation, as depicted in Figure 1.  The disease infects bats in the winter months when the bats are hibernating and in close contact with each other.  Some bats will survive the disease, while others will die of the infection.  The bats will begin to recover during summer since they are outdoors more.  When they return the following winter for hibernation, they risk infection again (Hoyt et al., 2021).

Figure 1: How Whtie-Nose Syndrome Spreads

(Hoyt et al., 2021)

            The disease affects bats the most during the winter when they are in their hibernation state.  They are vulnerable during hibernation because it makes them active while attempting to conserve energy (White-nose Syndrome Response Team, What Is White-nose Syndrome?). Figure 2 depicts the disease’s physiological effects on bats. The disease starts by causing damage to the bat’s tissue, increasing the bat’s metabolic rates.  An accelerated metabolic rate can cause the temperature of the bats to rise, leading to dehydration and loss of vital electrolytes. Additionally, the metabolic rate increase leads to energy reserve loss and fat reduction.  These factors combined have led to the increased mortality of multiple bat species (Hoyt et al., 2021).

 

Figure 2: Physiological Effects of White-Nose Syndrome on Bat Populations

(Hoyt et al., 2021)

Many different efforts are being made to help slow down the spread of the disease.  One such team, the White-Nose Syndrome Response Team, implements these conservation efforts to save multiple species of bats.  One such method is biological, which involves applying a bacterium to the bats known as Rhodococcus rhodochrous. This bacterium has features that help kill the disease.  The team uses different chemicals to kill the disease and prevent its spread. An example of this is Polyethylene glycol (PEG) 8000.  Progress is being made to create a vaccine for the bats.  Scientists are also changing habitat conditions, such as the temperature, to make it less ideal for the disease to grow (White-nose Syndrome Response Team. Helping Bats Survive).

Citations

Hoyt JR, Kilpatrick AM, Langwig KE (2021) Ecology and Impacts of White-Nose Syndrome on Bats. Nature Reviews Microbiology. 19: 196–210.

White-nose Syndrome Response Team. What Is White-nose Syndrome? https://www.whitenosesyndrome.org/static-page/what-is-white-nose-syndrome ((date last accessed 2 April 2024)

White-nose Syndrome Response Team. Helping Bats Survive. https://www.whitenosesyndrome.org/static-page/helping-bats-survive ((date last accessed 2 April 2024)

The Ocean Deep: Starving Oarfish or Climate Change?

It’s common knowledge that Oarfish of the family Regalecidae are cool, but we still know very little about them (Bester, 2017). It’s also common knowledge at this point that anthropogenic (or man-made) greenhouse gasses may have some effect on climate (Crowley, 2002).  As a result, the political and scientific realms have been furiously looking for ways to decrease carbon dioxide (CO2) emissions for decades, and debates have raged. One proposed solution from around the turn of the century was simply to pump the extra CO2 into the deep ocean, where it could be safely stored in the water column until photosynthetic creatures could dispose of it, or at least where it would stay and not cause any more progression in climate change (Seibel and Walsh, 2002). This seems on the surface like a perfect solution: the ocean is enormous and could easily store anthropogenic CO2. However, after studies were conducted on the physiological effects on deep sea creatures, the method was ruled far too environmentally detrimental. So, what could be happening that outweighs the impacts of climate change, and what does it have to do with Oarfish?

Well, first it’s important to understand a few physiology concepts. First is Metabolism, or the process by which organisms use Oxygen (O2) and a carbon-based fuel source (usually derived from food) to create Adenosine Triphosphate (ATP), which is the chemical that powers most cells, and CO2. This process, like all chemical processes, is dependent on the concentrations of the reagents, temperature, and pH among others, and is critical to sustaining life (Randall et al., 2002).

Second is respiration: the exchange of gasses necessary for an organism to continue metabolic processes. The process relies on 3 basic things: a good surface area over which to conduct exchange, a higher environmental partial pressure of O2 (and lower partial pressure of CO2) than that of the circulatory fluid entering the exchange area, and the ability of the organism to move that O2 through its body. Aquatic organisms accomplish this with gills, which provide ample surface area in their folds for gas diffusion to occur, and often with blood just like ours that contains Hemoglobin, the chemical that turns blood red when exposed to air. It is also responsible for binding and transporting absorbed O2 through the body. Hemoglobin is extremely sensitive to pH, and its oxygen binding power is easily changed by fluctuating pH, although this is often very species specific (Randall et al., 2002).

So, if we were to pump CO2 into the deep ocean, what would occur? Well, with the CO2 levels higher outside the organisms than inside, diffusion of CO2 wouldn’t be able to occur as easily, which would lead to a build-up of CO2 in the organism’s circulatory system. This would increase the pH of the fluid in the system (because dissolving CO2 in a fluid renders that fluid more acidic, just like the difference between flat pop and fizzy pop), rending Hemoglobin unable to bind to O2 as effectively. Finally, the lack of O2 would then lead to a lack of ATP in the organism via an inability to metabolize foods, and a decrease in the organism’s ability to do much of anything, often including live. This is much more acutely visible in deep sea creatures as hundreds of years of evolution under low light conditions have led to much slower predator-prey interactions, which has also lead, in combination with lower temperatures, to lower metabolic rates and lessened abilities to deal with pH changes (Seibel and Walsh, 2002). As little as a 0.2 reduction in pH is often enough to wipe out 50% of the zooplankton species in an area, which can cause serious food-chain issues in the deep sea as zooplankton often compose the base of oceanic food chains (Seibel and Walsh, 2002). Causing food chain issues could lead to a loss of biodiversity (Dudgeon et al., 2006), and given we know so little about the deep ocean, this could cost us huge. As an example, the Oarfish family of fishes are zooplankton filter feeders (Bester, 2017). They and so many more could be lost if we were to sequester CO2 at the bottom of the sea.

In conclusion, as tempting as it would be to just go ahead and save ourselves from climate change, we would do so at the cost of the biodiversity of the sea floor, and that’s simply not worth is as biodiversity is such an important factor of an ecosystem to preserve for economic, biomedical, and water quality reasons, among more (Dudgeon et al., 2006), and such actions would surely result in at the very least some loss of biodiversity (Seibel and Walsh, 2002). While it may yet be important to reduce climate change, certainly just pumping it to the bottom of the ocean isn’t the best way to solve that problem. After all, Oarfish need to eat too, and once again, your flappy friends thank you.

 

References:

Bester, Cathleen (2017) Regalecus glesne. Florida Museum, University of Florida. Retrieved 04/18/2017 from: https://www.flmnh.ufl.edu/fish/discover/species-profiles/regalecus-glesne/

Crowley TJ (2002) Causes of Climate Change Over the Past 1000 Years. Science 289(5477), 270. doi: 10.1126/science.289.5477.270

Dudgeon D, Arthington AH, Gessner MO, Kawabata ZI, Knowler DJ, Leveque C, Naiman RJ, Prieur-Richard RH, Soto D, Stiassny MLJ, Sullivan CA (2006) Freshwater Biodiversity: Importance, Threats, Status and Conservation Challenges. Biol Rev 81, 163-182.

Seibel BA, Walsh PJ (2002) Biological impacts of deep-sea carbon dioxide injection inferred from indices of physiological performance. J Exp Biol 206, 641-650. doi: 10.1242/jeb.00141

Randall JD, Burggren W, French K (2002) Eckert Animal Physiology. W. H. Freeman and Company, New York, pp 215–275.

Photos:

Feature Photo: An illustration of an oarfish, which can grow up to 17 meters in length. Source: Catalina Island Marine Institute.

In-Text Photos: Beached oarfish from Isla San Fransico beach. Source: Un-cruise.com/Barcroft USA. Retrieved from: http://www.dailymail.co.uk/news/article-2601475/Giant-Oarfish-dead-beach-just-days-rare-species-filmed-swimming-Mexico.html